Transforming growth factor-beta induces senescence in hepatocellular carcinoma cells and inhibits tumor growth

Authors

  • Serif Senturk,

    1. BilGen Research Center and Department of Molecular Biology and Genetics, Bilkent University, Ankara, Turkey
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  • Mine Mumcuoglu,

    1. BilGen Research Center and Department of Molecular Biology and Genetics, Bilkent University, Ankara, Turkey
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  • Ozge Gursoy-Yuzugullu,

    1. BilGen Research Center and Department of Molecular Biology and Genetics, Bilkent University, Ankara, Turkey
    2. Centre de Recherche, Institut National de la Santé et de la Recherche Médicale (INSERM)-Université Joseph Fourrier U823, Institut Albert Bonniot, La Tronche, France
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  • Burcu Cingoz,

    1. BilGen Research Center and Department of Molecular Biology and Genetics, Bilkent University, Ankara, Turkey
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  • Kamil Can Akcali,

    1. BilGen Research Center and Department of Molecular Biology and Genetics, Bilkent University, Ankara, Turkey
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  • Mehmet Ozturk

    Corresponding author
    1. BilGen Research Center and Department of Molecular Biology and Genetics, Bilkent University, Ankara, Turkey
    2. Centre de Recherche, Institut National de la Santé et de la Recherche Médicale (INSERM)-Université Joseph Fourrier U823, Institut Albert Bonniot, La Tronche, France
    • Centre de Recherche INSERM/UJF U823, Institut Albert Bonniot, Grenoble, France
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    • Fax: +33476549413


  • This work was supported by grants from the TUBITAK and State Planning Office (Turkey) and the Institut National de Cancer (France). Additional support was provided by the Turkish Academy of Sciences.

  • Potential conflict of interest: Nothing to report.

Abstract

Senescence induction could be used as an effective treatment for hepatocellular carcinoma (HCC). However, major senescence inducers (p53 and p16Ink4a) are frequently inactivated in these cancers. We tested whether transforming growth factor-β (TGF-β) could serve as a potential senescence inducer in HCC. First, we screened for HCC cell lines with intact TGF-β signaling that leads to small mothers against decapentaplegic (Smad)-targeted gene activation. Five cell lines met this condition, and all of them displayed a strong senescence response to TGF-β1 (1-5 ng/mL) treatment. Upon treatment, c-myc was down-regulated, p21Cip1 and p15Ink4b were up-regulated, and cells were arrested at G1. The expression of p16Ink4a was not induced, and the senescence response was independent of p53 status. A short exposure of less than 1 minute was sufficient for a robust senescence response. Forced expression of p21Cip1 and p15Ink4b recapitulated TGF-β1 effects. Senescence response was associated with reduced nicotinamide adenine dinucleotide phosphate oxidase 4 (Nox4) induction and intracellular reactive oxygen species (ROS) accumulation. The treatment of cells with the ROS scavenger N-acetyl-L-cysteine, or silencing of the NOX4 gene, rescued p21Cip1 and p15Ink4b accumulation as well as the growth arrest in response to TGF-β. Human HCC tumors raised in immunodeficient mice also displayed TGF-β1–induced senescence. More importantly, peritumoral injection of TGF-β1 (2 ng) at 4-day intervals reduced tumor growth by more than 75%. In contrast, the deletion of TGF-β receptor 2 abolished in vitro senescence response and greatly accelerated in vivo tumor growth. Conclusion: TGF-β induces p53-independent and p16Ink4a-independent, but Nox4-dependent, p21Cip1-dependent, p15Ink4b-dependent, and ROS-dependent senescence arrest in well-differentiated HCC cells. Moreover, TGF-β–induced senescence in vivo is associated with a strong antitumor response against HCC. HEPATOLOGY 2010

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